Characterization of melatonin binding to the anteroventral and anterodorsal thalamic nuclei of the rat.

Binding of 2-[125I]melatonin to the anteroventral and anterodorsal nuclei of the rat limbic thalamus was analyzed with in vitro autoradiography. In both nuclei the binding was of high affinity (Kd values 24-41 pM) and was competed with by nanomolar concentrations of 6-hydroxymelatonin. Kd values were in the same range as those reported for other high-affinity binding sites in the brain. Bmax values were 0.68-2.99 fmol/mg protein. The results suggest that some effects of melatonin are mediated via the limbic thalamus.